The underlying molecular events governing the genetic control of the inducible photosynthetic membrane system found in the facultative nonsulfur-purple phototrophic Rhodopseudomonas sphaeroides, are the subject of this investigation. Results, recently obtained are described in detail and cover: the cloning of specific genetic regionality a combination of in vivo and in vitro techniques, the extension of our ability to employ conventional genetic analyses in R. sphaeroides and the development of alternative approaches to the isolation of mutants blocked in various steps in the structure and function of the photosynthetic membrane. Future experiments are proposed which continue and greatly expand the approaches outlined above. These include the utilization of Mudl(lac. Apr) fusions and transposon-induced mutants which have already been isolated as a means of obtaining genetic regions controlling specific photosynthetic membrane functions. Our ability to transform R. sphaeroides, together with the development of an in vitro coupled transcription-translation system facilitate studies of the cryptic plasmids present in R. sphaeroides, particularly the 30 Mdalton plasmid which may be implicated in photosynthetic function and further allow us to return to R. sphaeroides, genetic regions of interest and which have been isolated. The development of plasmid, Lamda and cosmid banks of R. sphaeroides DNA are useful in those studies outlined above and further permit us to address the general question of the apparent lack of expression of R. sphaeroides DNA in E. coli. Finally, more conventional genetic approaches are anticipated and which should further permit the general description of the genetics of photosynthetic membrane development, structure and function. A full understanding of the genetics of photosynthetic membrane structure and function in R. sphaeroides is essential to our general understanding of membranes. Further, and understanding of the functional relationship between the mitochondrion and R. sphaeroides may be facilitated by a genetic study of electron transport and membrane development in R. sphaeroides. Lastly, the effect of light and oxygen on biological tissue are singular significance.